A trocar assembly is a surgical instrument that is used to gain access to a body cavity. A trocar assembly generally comprises two major components, a trocar tube and an obturator. The trocar tube having the obturator inserted therethrough is directed through the skin to access a body cavity through the tube in which laparoscopic or arthroscopic surgery and endoscopic procedures are to be performed. In order to penetrate the skin, the distal end of the trocar tube is placed against the skin which has been cut with a scalpel. The obturator has a sharp point or cutting edge at its distal end. By applying pressure against the proximal end of the obturator, the sharp point is forced through the skin until it enters the body cavity. The trocar tube is inserted through the perforation made by the obturator and the obturator is withdrawn, leaving the trocar tube as an accessway to the body cavity. Examples of trocar assembly devices are disclosed in U.S. Pat. No. 4,535,773.
The proximal end portion of the trocar tube is typically adjoined by a housing that defines a chamber having an open distal end portion that communicates with the interior lumen defined by the trocar tube. An obturator and other elongate surgical instruments or tools axially extend into and are withdrawn from the trocar tube through the proximal end portion of the chamber. It is the present practice to provide the chamber with a sealing means, such as a sealing grommet or gasket, through which the obturator or other instruments extend. The sealing means seals against the outer surface of the inserted instruments and thereby prevents fluids and insufflation gas from leaving or entering the body cavity through the trocar tube.
It is typically necessary to manipulate a surgical instrument extending through the trocar assembly during a surgical procedure. In so doing, the off-centering or non-axial orientation of the instrument as it extends through the sealing means may prevent the sealing means from maintaining sealing engagement with the instrument. Accordingly, there is a need for a trocar assembly that includes a sealing means that maintains sealing engagement with an instrument extending therethrough during off-centering of the instrument. It is also desirable for the sealing means to include means to guide an instrument extending therethrough in a manner that minimizes insertion and drag forces as the instrument is inserted and withdrawn from the trocar assembly.